helium hood method

I have the helium party tanks and the hood. My question which I have asked before is what happens when the helium runs out. For example. I bought a tank and turned it on full. The helium came out pretty quick and I was firstly unsure if the helium would blow off the hood which I had read in another site?  However I was also wondering because the gas ran out within minutes. So I was wondering if it would be equally effective if the gas was released more slowly? i.e dont turn the nozzle all the way round.  Would this still keep the required supply to the hood? Also after someone becomes unconscious ( a few seconds ), it will take around 5-10 minutes before death. What happens if the helium tanks run out. Do you still keep or re-breath the helium in the hood? I have seen that two party balloon kit tanks are the required amounts. So in essence, not forgetting the above questions,  if you follow all the instructions, even though you have the hood on with the helium inside, what happens when the helium runs out?